U.S. patent number 6,424,285 [Application Number 09/341,028] was granted by the patent office on 2002-07-23 for communications system for remote control systems.
This patent grant is currently assigned to Thomson Licensing S.A.. Invention is credited to Michael Kelly Perdue, Michael Anthony Pugel, James Allen Strothmann.
United States Patent |
6,424,285 |
Perdue , et al. |
July 23, 2002 |
Communications system for remote control systems
Abstract
A communications system for transmitting and receiving remote
control messages in an electronic remote control system. The
present communications system uses a remote control message
protocol which is particularly suitable for transmitting RF remote
control messages with IR remote control messages in a time
multiplexed fashion, wherein the RF remote control messages are
transmitted during the pause intervals between IR remote control
message transmission intervals. The present remote control message
protocol includes a start sequence, comprising a MARK pulse and a
SPACE of about equal duration, followed by a plurality of data
fields. Each data field ends with an End of Field marker and the
remote control message ends with an End of Message marker. The
plurality of data fields comprises an addressing data field for
specifying the destination device, a security code data field for
allowing a specific remote control transmitter to control a
specific destination device, a status field for specifying various
status codes associated with the remote control message, a keycode
field for carrying the remote control message payload, and a
checksum field for verifying the transmission integrity of the
remote control message. A remote control message based on the
present message protocol may be expanded to include additional data
fields and to expand pre-existing data fields.
Inventors: |
Perdue; Michael Kelly
(Indianapolis, IN), Strothmann; James Allen (Indianapolis,
IN), Pugel; Michael Anthony (Noblesville, IN) |
Assignee: |
Thomson Licensing S.A.
(Boulogne, FR)
|
Family
ID: |
26713502 |
Appl.
No.: |
09/341,028 |
Filed: |
November 12, 1999 |
PCT
Filed: |
January 30, 1998 |
PCT No.: |
PCT/US98/01858 |
371(c)(1),(2),(4) Date: |
November 12, 1999 |
PCT
Pub. No.: |
WO98/34208 |
PCT
Pub. Date: |
August 06, 1998 |
Current U.S.
Class: |
341/176;
398/106 |
Current CPC
Class: |
G08C
23/04 (20130101); G08C 17/02 (20130101); G08C
2201/63 (20130101) |
Current International
Class: |
G08C
19/12 (20060101); H04L 17/00 (20060101); H04L
17/02 (20060101); G08C 019/12 (); H04L
017/02 () |
Field of
Search: |
;341/176 ;345/169
;348/735 ;340/825.69,825.72 ;379/102.01,102.03 ;359/142,145 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0721282 |
|
Jul 1996 |
|
EP |
|
96/36954 |
|
Nov 1996 |
|
WO |
|
Other References
PCT Search Report dated Jun. 29, 1998..
|
Primary Examiner: Edwards; Timothy
Attorney, Agent or Firm: Tripolo; Joseph S. Kiel; Paul
P.
Parent Case Text
This application claims benefit of provisional application Nos.
60/036,794, filed Jan. 31, 1997 and 60/038,893, filed Feb. 20,
1997.
Claims
What is claimed is:
1. A remote control apparatus, comprising: an input device for
receiving remote control messages from a user; a signal
transmitter; and a controller operatively coupled to said input
device and said signal transmitter, said controller generating a
remote control message and causing said signal transmitter to
transmit said remote control message in response to the user input,
said remote control message comprising start sequence followed by a
plurality of data fields, each said data field ending with an end
of field marker, said plurality of data fields including a status
field having a message type identifier which identifies a
particular message protocol, and a keycode data field carrying
keycode data, said keycode data formatted in accordance with said
particular message protocol.
2. The remote control apparatus of claim 1, wherein said keycode
data comprises one of a standard remote control protocol formatted
data and ASCII character data.
3. The remote control apparatus of claim 1, wherein said start
sequence comprises a pulse and a pause period having substantially
equal duration.
4. The remote control apparatus of claim 1, wherein said remote
control message further comprises an expansion data field and an
end of message marker, said controller transmitting said remote
control message in the order of, said start sequence, said
plurality of data fields, said expansion data field, and said end
of message marker.
5. The remote control apparatus of claim 1, wherein said remote
control message further comprises a field expansion data field
associated with one of said plurality of data fields and an end of
message marker, said controller transmitting said field expansion
data field immediately prior to said associated data field.
6. The remote control apparatus of claim 1, wherein said signal
transmitter is a RF signal transmitter.
7. The remote control apparatus of claim 6, wherein said plurality
of data fields further comprises a preamble field having data for
addressing a destination device, a security code field having an
identifier associated with said signal transmitter, and a checksum
field for verifying transmission integrity of said remote control
message.
8. The remote control apparatus of claim 7, wherein said security
code data comprises a three digit code programmed into said
controller by the user.
9. The remote control apparatus of claim 7, wherein said controller
generates said remote control message using leading zero
suppression.
10. The remote control apparatus of claim 9, wherein said security
code data is programmed into said controller using an On Screen
Display menu.
11. A remote control system, comprising: an input device for
receiving remote control messages from a user; an IR signal
transmitter; a RF signal transmitter; and a controller operatively
coupled to said input device, said IR signal transmitter and said
RF signal transmitter, said controller generating an IR remote
control message having pause intervals and a RF remote control
message, said RF remote control message comprising a start sequence
having a pulse and a pause period having substantially equal
duration followed by a plurality of data fields, each said data
field ending with an end of field marker, said plurality of data
fields including a status field having a message type identifier
which identifies a particular message protocol, and a keycode data
field carrying keycode data, said keycode data formatted in
accordance with said particular message protocol, said controller
causing said IR signal transmitter and said RF signal transmitter
to transmit said IR and RF remote control messages, wherein said RF
remote control message is transmitted during the pause intervals of
said IR remote control message.
12. The remote control apparatus of claim 11, wherein said keycode
data comprises one of a standard remote control protocol formatted
data and ASCII character data.
13. The remote control apparatus of claim 11, wherein said RF
remote control message is transmitted in the order of, said start
sequence, a preamble field having data for addressing a destination
device, a security code field having an identifier associated with
said signal transmitter, said status field, said keycode field, a
checksum field for verifying transmission integrity of said RF
remote control message and an end of message marker.
14. The remote control apparatus of claim 13, wherein said
controller generates said RF remote control message using leading
zero suppression.
15. The remote control apparatus of claim 13, wherein said security
code data comprises a three digit code programmed into said
controller by the user.
16. The remote control apparatus of claim 15, wherein said security
code data is programmed into said controller using an On Screen
Display menu.
17. A method of transmitting a remote control message, comprising
the steps of: receiving a user input through an input device;
generating an IR remote control message associated with the user
input, the IR remote control message having pause intervals;
generating a RF remote control message corresponding to the user
input, the RF remote control message comprising a start sequence
having a pulse and a pause period having substantially equal
duration followed by a plurality of data fields and an end of
message marker, each said data field ending with an end of field
marker, said plurality of data fields comprising a status field
having a message type identifier which identifies a particular
message protocol, and a keycode data field having keycode data
formatted in accordance with the particular message protocol; and
transmitting the IR and RF remote control messages by transmitting
the RF remote control message during the pause intervals of the IR
remote control message.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a communications system, and more
particularly to a communications system for transmitting and
receiving remote control messages to control electronic
devices.
A variety of remote control systems that transmit and receive
remote control messages to control various electronic devices are
known. Such systems typically include a remote control device which
comprises an input device, such as a keypad, for allowing user
input, coupled to a controller which is in turn coupled to a signal
transmitter. In response to a user input, the controller generates
an appropriate remote control message using look up tables, and the
like, from memory and causes a signal transmitter to transmit the
remote control message. The signal transmitter may be designed to
transmit the remote control message in a number of different forms,
including, but not limited to, an IR signal and a RF signal.
One commonly used method of sending a remote control message is to
transmit the message in IR signal form. Remote control devices that
transmit IR signals are well known and commonly used with household
electronic devices. The message format of the IR signal is
determined by the manufacturer for each model and many such IR
message formats are known and used. Each format specifies a set of
message characteristics, which include, but are not limited to
message duration, transmission and pause intervals and types of
data carried in the remote control message.
However, there are several disadvantages associated with using IR
signals to control an electronic device. First, the IR signal is
directional and as such requires the user to point the remote
control device toward the destination device for proper
transmission performance. Also, the IR signal may have a relatively
short range and be easily blocked by objects such as walls, floors,
ceiling and the like, so a remote control device must generally be
used in the same room in which the destination device is
located.
Also, many existing IR signal message formats do not have
sufficient data carrying capacity to transmit all of the different
types of remote control data required for controlling many modern
electronic devices. For example, in addition to the conventional
remote control messages associated with household electronic
devices, such as ON, OFF, Channel Up, Channel Down, etc., many
modern electronic devices, such as satellite receivers, may require
the remote control device to send other forms of data, such as
ASCII character data. Many existing IR signal message formats are
not designed to handle such additional forms of data and/or simply
do not include enough capacity to carry the data.
Another method of sending a remote control message is to transmit
the message in RF signal form. RF signals are generally
non-directional and have greater range than IR signals. RF signals
may also be transmitted through objects such as walls, and the
like, so that the user can use the remote control device to control
a device in a separate room. This extended range and ability to
transmit messages through objects is beneficial in situations where
a central device, such as a set top box or a satellite receiver,
provides input to a plurality of devices located throughout
different rooms in a building. Also, RF signal message formats
generally have wider bandwidths, and thus have greater data
carrying capacity, than existing IR signal formats.
As such, it is desirable to be able to use RF signals to control
modern electronic devices. However, devices and methods using IR
signals remain popular and are widely used. In order to maintain
backward compatibility, i.e., allow a remote control device to
control existing devices which utilize IR signals, a remote control
device should also be capable of transmitting IR signals.
Therefore, it is desirable to have an apparatus and a method for
easily and efficiently transmitting some combination of IR and RF
signals to take advantage of the features of the two signal
transmission forms.
However, existing IR signal message formats, or protocols, are not
totally suitable for transmitting remote control messages in RF
form. Since, the RF signals have longer range and transmit through
objects better than IR signals, a RF signal message format must
include a method of preventing interference from neighboring RF
signal transmitters. Also, existing IR signal message formats do
not allow a remote control device to send different types of data,
such as ASCII data, in addition to the standard IR signal commands.
Further, existing IR signal message formats do not take full
advantage of the increased bandwidth and expandability associated
with RF signals. Limited use of the available bandwidth and limited
expandability reduces the ability to efficiently transmit and
receive additional data, as well as more complex data, thereby
limiting the ability to add new types of remote control devices to
an existing system and incorporate new features to existing remote
control devices.
SUMMARY OF THE INVENTION
Therefore, what is needed is a communications system for use in a
remote control system which provides for increased data carrying
capacity and expandability. In particular, what is needed is a
communications system which uses a message protocol that provides
for the ability to efficiently transmit and receive an increased
amount of data, as well as different types of data, compared to
existing remote control message protocols. Further, what is
required is a message protocol which can be expanded to carry an
additional amount of data and/or more types of data, yet remain
both forward and backward compatible with existing and future
receiver/decoders.
The present invention involves a communications system that uses a
message protocol which provides for the transmission and receipt of
complex data, as well as different types of data, such as ASCII
data, and allows for expansion of the message as required, in an
efficient format. The present communications system and message
protocol is suitable for transmitting and receiving remote control
messages in RF signal form, and especially suitable for
transmitting and receiving a RF signal in combination with an IR
signal by time multiplexing the two signals.
In accordance with one aspect of the present invention a remote
control apparatus is provided, comprising an input device for
receiving remote control messages from a user, a signal
transmitter, and a controller operatively coupled to the input
device and the signal transmitter, the controller generating a
remote control message and causing the signal transmitter to
transmit the remote control message in response to the user input,
the remote control message comprising a plurality of data fields,
each of the data field ending with an end of field marker, the
plurality of data fields comprising a status field having signal
transmission information including a keycode type bit, and a
keycode field having one of first and second data in accordance
with a state of the keycode type bit.
In accordance with another aspect of the present invention, a
remote control system is provided, comprising an input device for
receiving remote control messages from a user, an IR signal
transmitter, a RF signal transmitter and a controller operatively
coupled to the input device, the IR signal transmitter and the RF
signal transmitter, the controller generating an IR remote control
message and a RF remote control message and causing the IR signal
transmitter and the RF remote signal transmitter to transmit the IR
and RF remote control messages, respectively, in a time multiplexed
manner in response to the user input, the RF remote control message
comprising a plurality of data fields, each of the data fields
ending with an end of field marker, the plurality of data fields
comprising a status field having signal transmission information
including a keycode type bit, and a keycode field having one of
first and second data in accordance with a state of the keycode
type bit.
In accordance with another aspect of the present invention, a
remote control apparatus is provided comprising an input device for
receiving remote control messages from a user, a signal
transmitter, and a controller operatively coupled to the input
device and the signal transmitter, the controller generating a
remote control message and causing the signal transmitter to
transmit the remote control message in response to the user input,
the remote control message comprising a start sequence comprising a
pulse and pause period having about equal duration, a preamble
field having data for addressing a destination device, a security
code field having an identifier associated with said signal
transmitter, a status field having signal transmission status
information, a keycode field having either a first or second data
in accordance with a keycode type bit in the status field, a
checksum field for verifying transmission integrity of the remote
control message and an end of message marker.
In accordance with another aspect of the present invention, a
remote control apparatus is provided comprising a signal receiver
adapted to receive a remote control message, a controller
operatively coupled with the signal receiver, the controller
adapted to decode and process the remote control message, the
remote control message comprising a plurality of data fields, each
of the data fields ending with an end of field marker, the
plurality of data fields comprising a status field having signal
transmission information including a keycode type bit, and a
keycode field having one of first and second data in accordance
with a state of the keycode type bit.
In accordance with another aspect of the present invention, a
method of transmitting a remote control message is provided
comprising the steps of: receiving a user input; generating a
remote control message corresponding to the user input, the remote
control message comprising a start sequence followed by a plurality
of data fields and an end of message marker, each of the data
fields ending with an end of field marker, the plurality of data
fields comprising a preamble field having data for addressing a
destination device, a security code field having an identifier
associated with the remote control apparatus, a status field having
transmission status information about the remote control message, a
keycode field having data associated with the user input and a
checksum field for verifying transmission integrity of the remote
control message; and applying the remote control message to a
signal transmission circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described with reference to the accompanying
drawings, wherein:
FIG. 1 is a block diagram showing the elements of a remote control
device suitable for use in the present communications system;
FIG. 2 is a block diagram illustrating the basic elements of a
suitable RF signal transmitter;
FIG. 3 is a block diagram illustrating the basic elements of a
suitable RF signal receiver;
FIG. 4 is an illustration of a transmission sequence of IR and RF
remote control messages wherein the IR and RF messages are
transmitted in time multiplexed manner;
FIG. 5 is an illustration of the data fields in a remote control
message protocol of the present communications system;
FIG. 6 is an illustration of the waveform of the MARK and SPACE
portions of the remote control message protocol;
FIG. 7 is an illustration of a waveform of a symbol in the remote
control message protocol;
FIG. 8 is an illustration of a waveform of a remote control message
using leading zero suppression;
FIG. 9 is an illustration of adding a new data field in the remote
control message protocol;
FIG. 10 is an illustration of expanding a pre-existing field in the
remote control message protocol;
FIG. 11 is an illustration of using leading zero suppression when
expanding a pre-existing field in the remote control message
protocol;
FIG. 12 is a block diagram illustrating the basic elements of a
signal receiver/decoder suitable for use in the present
communications system; and
FIG. 13 is a flowchart diagram illustrating the steps of a
debouncing method.
DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT
Referring to FIG. 1, there is shown a simplified block diagram of
remote control 10 suitable for use with the present communications
system. Remote control 10 may take many forms, such as a stand
alone unit or a portion of a larger communications device, and be
adapted for use with a variety of electronic devices. For example,
devices which incorporate the elements and signal transmission
features of remote control 10 include, but are not limited to, a
wireless keyboard, wireless pointing devices and handheld remote
control devices for controlling consumer electronic devices. It is
to be understood that the present remote control may be used with
any system adapted to transmit, receive or process remote control
messages in response to a user input.
Generally, user input is received through input device 20 which
includes various control buttons, device selection buttons,
numerical buttons and the like. It is to be understood that input
device 20 may include any device whereby the user can provide an
input to remote control 10 and includes, but is not limited to, a
keypad matrix, mouse, trackball, joystick and other types of
pointing devices. Input device 20 is operatively coupled to
controller 14 which controls the overall operation of remote
control 10. Controller 14 receives the user input, and generates
and causes the transmission of an appropriate remote control
message. Controller 14 may comprise any one of a plurality of
conventionally known devices, which may be in integrated circuit
form, that are capable of performing control functions. Suitable
controllers include, but are not limited to ST 7291 and ST 7225
manufactured by SGS Thomson Microelectronics. The timing of
controller 14 is controlled by crystal oscillator 18.
Upon receiving a user input from input device 20, controller 14
uses the designated reference code, or other identifying
information to look up the desired information from the product
code look up tables stored in memory 22 in order to identify and
generate a remote control message having the correct signal
structure. The signal structure characteristics include, but are
not limited to, the proper carrier frequency, pulse width, pulse
modulation and overall signal timing information. Memory 22 may
comprise RAM and/or ROM and be located either internal or external
to an enclosure associated with remote control 10. Controller 14
applies the appropriate remote control signal to IR transmitter 16
and/or RF transmitter 17 to send the signal to the destination
device. Controller 14 also controls display 12, which may include,
for example, indicator LEDs, to indicate that a remote control
message has been transmitted. When the remote control message is
transmitted, an IR receiver and/or a RF receiver associated with
the destination device detects the remote control message and
provides the message to the processor of the destination device for
decoding and processing.
FIGS. 2 and 3 show RF transmitter 40 and RF receiver 50,
respectively, suitable for use in sending and receiving RF messages
in the present communications system. As shown in FIG. 2, RF
transmitter 40 comprises bipolar oscillator 46 with a one-port SAW
resonator for frequency stabilization coupled to mixer 44, which
drives a linearly polarized loop antenna 48 which is typically
located in the enclosure of remote control 10. When the user
provides an input, for example by pressing a key, controller 14
generates a modulating signal which is used to turn oscillator 46
ON and OFF for amplitude shift keying of the carrier. It is
generally desirable that transmitter 40 include minimal parts due
to limited space in the enclosure of remote control 10.
A suitable RF receiver 50 is shown in FIG. 3. RF receiver 50 will
typically be located in, or connected to, the enclosure of the
destination device. The receiver is capcitively coupled to antenna
52, which may advantageously be a line cord that acts as a receive
antenna, in which case the RF signal enters through a connector
disposed on the enclosure around RE receiver 50. The signal is
amplified by low-noise amplifier 54, which decreases the total
system noise level while increasing receiver sensitivity. The
output of amplifier 54 passes through image filter 56 which
provides rejection to the image frequency. The signal is then
converted via mixer 58 and local oscillator 60 to an intermediate
frequency (IF) of 10.7 MHz. The IF signal is passed through filter
62 and amplified by a chain of high gain logarithmic amplifiers 64
which convert the signal into an output current. The output current
is converted to a voltage, passed to a noise adaptive threshold
comparator 66, and lowpass filtered by data filter 68 before being
sent to the processor of the destination device for decoding and
processing.
Any one of a number of conventionally known IR transmitter and IR
receiver arrangements may be used to send and receive IR remote
control messages in the present invention. Generally, an IR
transmitter includes an LED coupled to an LED driver circuit which
is controlled by controller 14. In response to a user input,
controller 14 generates an IR remote control signal in accordance
with the look up table in memory 22 and applies the IR remote
control signal to the LED driver circuit. The LED driver circuit
drives the LED to project an IR signal toward the controlled
device. An IR light sensor in the IR receiver detects the IR signal
and provides the signal to a processor in the destination device
for decoding and processing. Suitable IR and RF transmitter and
receiver arrangements include, but are not limited to, those found
in DSS System DS5450RB manufactured by Thomson Consumer Electronics
Inc., of Indianapolis, Ind.
Remote control 10 transmits the IR signal, the RF signal or any
combination thereof for controlling an electronic device in
response to user input. Advantageously, in order to transmit both
an RF signal and an IR signal for each user input, wherein each
signal is generated according to a respective message protocol,
remote control 10 may transmit the two messages in a time
multiplexed manner. In particular, the IR and RF signals may be
transmitted in alternating fashion with the RF signal transmitted
during the pause interval of the IR signal as shown in FIG. 4. In
signal transmission sequence 70, the IR signals are transmitted
during intervals 74 and 78 while the RF signals are transmitted
during pause intervals 72 and 76.
The transmission sequence described above is particularly suitable
for use with existing IR signal protocols as such protocols usually
require repeated intervals of IR signal transmission interrupted by
pause intervals. RF signals can easily be transmitted during the
pause intervals without affecting the IR signal transmissions.
Typically, the pause interval between the IR transmissions lasts
between 2-10 mS. Such a sequence may be implemented using
relatively inexpensive controllers. An apparatus and a method for
transmitting IR and RF messages in such a manner is described in
co-pending U.S. patent application Ser. No. 09/331,996, entitled
"Remote Control Apparatus and Method" which is assigned to the
assignee of the present application.
The present communications system uses a remote control message
protocol which is particularly suitable for transmitting RF remote
control messages in the above-described multiplexed manner. The
data field structure and associated timing of the present remote
control message protocol allow a RF message using the present
remote control message protocol to be easily transmitted in the
pause intervals as described above. However, it is to be understood
that the present remote control message protocol may be used with
any signal transmission media, such as IR transmissions, and may be
used for any message transmission method, and is not limited to use
in multiplexed transmission schemes.
The structure of the present remote control message protocol is
shown in FIG. 5. The remote control message 80 comprises a start
sequence comprising MARK/SPACE combination 82 followed by a
plurality of data fields. The illustrated remote control message
comprises five data fields. However, as described further below,
the number of data fields may be increased if the remote control
message needs to be expanded in order to encompass increased
functionality. Each field ends with End of Field (EOF) marker 85.
Use of an EOF marker allows the size of a particular field to
expand without changing the existing data fields in the message
protocol. The end of the message is marked by End of Message (EOM)
marker 87. Use of an EOM marker allows the number of fields
transmitted in the remote control message to be increased without
changing the existing data fields in the protocol. It can be seen
that use of EOF marker 85 and EOM marker 87 allows the present
message protocol to handle an increasing number of devices and
functions without altering existing RF systems in the field.
The format of MARK/SPACE combination 82 and the data within the
data fields are now described. The MARK/SPACE combination 82, as
shown in FIG. 6, signals the beginning of a new remote control
message and is used by the destination receiver to distinguish the
start of the message from pulses caused by background noise. MARK
pulse 102 is designed to be wider than the sync pulses that make up
the rest of the remote control message. The special length of MARK
pulse 102 and the following pause period, namely SPACE 104, allows
the receiver/decoder to recognize the beginning of the remote
control message from background noise and partial messages from
other remote control devices. Suitable timing for MARK pulse 102
and SPACE 104 are shown in table 1 below (units in uS):
TABLE 1 Minimum Typical Maximum MARK pulse width 90 100 110 SPACE
signal time 90 100 110
Following the MARK and SPACE, the signal transmitter transmits a
plurality of data fields. The data in each data field comprise a
plurality of symbols including: "1", "0", and EOF. The remote
control message ends with the EOM symbol. Each of the symbols
comprises a waveform comprising a sync pulse and a pause space, and
as shown in FIG. 7, waveform 105 is defined by sync pulse width 106
and total symbol time 108. Suitable values for the sync pulse width
106 and total symbol time 108 for each symbol are shown in table 2
below (units in uS, except EOM which is in mS):
TABLE 2 Minimum Typical Maximum Sync pulse width (all symbols) 45
50 55 "1" total symbol time 160 175 190 "0" total symbol time 210
225 240 EOF total symbol time 260 275 290 EOM total symbol time .30
65 infinite
Each data field contains 8 bits of data and is transmitted in the
order of least significant bit first to the most significant bit
last. The data fields also feature leading zero suppression to
reduce data transmission time, whereby any of the most significant
bits not transmitted for a particular byte when the EOF signal is
received are assumed to be "0". The structure and transmission
order, from left to right, of a sample data field is shown
below:
If the field has at least one most significant bit that is zero
(data byte less than 80 hex, bit 7 or more clear), then these
bit(s) would not be transmitted and an EOF marker is transmitted
after the final set bit. An EOM marker would replace the EOF marker
for the last field, signaling the receiver that no more fields are
forthcoming and processing of the message may begin.
An example of a remote control message that demonstrates the use of
leading zero suppression, as well as illustrates the use of the
various symbols described above, is shown in FIG. 8. In FIG. 8,
remote control message 110 comprises start sequence 112, followed
by data fields 113-116 and EOM marker 117. Data fields 113-116
transmit "0D", "00", "0E" and "3B" respectively. Byte "00" is
represented with only an EOF symbol, with all leading zero bits
suppressed. Also, EOM marker 117 replaces the EOF marker for the
last field 116.
The data associated with each of the data fields shown in FIG. 5 is
now described. The preamble field comprises an identifying code
associated with the destination device and is used to address the
destination device. The code data in the preamble field may
correspond to the preamble codes used in a pre-existing remote
control message protocol, for example Thomson Consumer Electronics,
Inc. Specification 15206770. All preamble fields for valid RF
devices should correspond with the assigned preambles per the
manufacturer's specifications. Advantageously, the preamble of
future RF compatible products may be designed to be addressable
using existing IR preamble codes.
The privacy code field comprises a 3 digit number in the range from
000-255 which is programmed into remote control device 10 by the
user and uniquely identifies the source of the remote control
message transmission. The privacy code allows the receiver to
respond only to the proper remote control device and messages
carrying incorrect privacy codes are ignored. The receiver for the
destination device includes its own use interface for determining
what privacy code to accept The privacy code feature is
particularly advantageous in RF signal transmission applications
for preventing neighboring RF transmitters from affecting the
destination device and the present remote control device from
affecting neighboring RF receivers. As such, the privacy code
feature is particularly beneficial in densely populated areas
wherein many other RF remote control devices may be operating. The
preamble and security code fields are transmitted first to allow
early rejection of the message by the destination device to improve
the performance of the system.
The privacy code feature also provides for additional addressing
capability if several receivers within range use the same preamble
code. For example, if a user wishes to control 4 Digital Satellite
System ("DSS") receivers wherein the DSS remote control which
includes keys for "DSS 1" and "DSS 2", a pair of DSS receivers may
be associated with "DSS 1" key and configured to respond to a first
and second privacy codes, respectively, and another pair of DSS
receivers may be associated with "DSS 2" key and configured to
respond to the first and second privacy codes, respectively.
Any conventionally known method for programming remote control
devices may be used to assign the security codes, for example, the
user may program the remote control device by pressing an
appropriate device key, for example, TV, VCR or DSS, and then
entering a security code, for example a three digit code.
Alternatively, the user may be guided through the programming
sequence by an appropriate user interface, for example, a menu on
an On Screen Display.
The status field provides status information about the remote
control message transmission and includes the following flags: Bit
7-Bit 2: currently unused Bit 1: Keycode type Bit 0: Keypress
status
The keycode type bit (bit 1) indicates that the data carried in the
keycode field is one of two types of data depending on the status
of bit 1, for example a standard Thomson Consumer Electronic
("TCE") keycode data or ASCII character data byte from an
alternative device, such as a keyboard, mouse, trackball, etc.
The keypress status bit (bit 0) toggles with each new key press on
remote control device 10. The keycode type bit, along with timing
of the message separation assists the receiver in determining
whether a message is a repeated message from a single keystroke or
the result of another key press on remote control device 10. As
described further below the keycode type bit is used in a
debouncing method to distinguish new keypresses of remote control
10 from old ones thereby preventing the receiver from performing
multiple responses to a single keypress on remote control device
10.
Bit 7 through bit 2 are reserved for future expansion and should
default to a "0" to take advantage of the leading zero suppression
feature of the present remote control message protocol.
The keycode data field includes the data associated with the user
input, such as a command or character data associated with a
particular key. The data carried in this field may comprise data of
any suitable format for transmitting the user input. In the present
remote control message protocol, the data carried in this field
comprises either a standard 8-bit keycode associated with a
pre-existing IR protocol, such as the Thomson Consumer Electronics,
Inc. Specification 15206770, or an ASCII character data byte
depending on the status of the keycode type bit in the status
field.
The checksum byte field is used to verify accurate receipt of the
remote control message for all fields in the remote control message
up to, but not including the checksum field. All fields preceding
the checksum field are summed using 8-bit addition and the result
is transmitted in the checksum field.
The present remote control message protocol may be modified to add
additional data to the message while maintaining forward and
backward compatibility with future remote control transmitters and
receivers. Modification of the present remote control message
protocol may be necessary, for example, to accommodate additional
electronic devices or additional functions for a particular
electronic device. The modification to the present remote control
message protocol may take many forms, including, but not limited
to, adding a new field of data, expanding a field beyond 8 bits,
and adding additional status bits.
Modification of the present remote control message protocol to add
a new data field is illustrated in FIG. 9. A new data field may be
required due to, for example, the addition of a new feature in
remote control device 10 or in the destination device. The new
field 152 is inserted between the existing data fields 151 and
checksum field 153, which is always the last field of the message.
The additional data field increases the overall length of the
remote control message, but does not affect existing data fields
151 of the remote control message. In this manner, the present
remote control message protocol may be easily modified to add
additional features and still be able to control destination
devices that are based on older versions of the protocol.
Modification of the present remote control message protocol to
expand a field size is illustrated in FIG. 10. Expansion of a field
may be necessary to accommodate, inter alia, additional types of
remote control devices and increased functionality of existing
remote control devices. If a field requires an increase in size
beyond 8 bits, a new field is added and placed immediately before
the original field that required expansion. In the example shown in
FIG. 10, expansion of the keycode field is realized by adding a
keycode high byte field 163 between status field 161, and keycode
field 162 and checksum field 164. If the expansion of the keycode
requires an increase from 8 to 10 bits, then the bits would be
transmitted in the order shown in FIG. 11. In such a case, bits 9
and 10 of the keycode high byte would be located in bit 0 and 1 of
the high byte field 171, respectively, while the remaining bits are
transmitted in field 172. Field 172 should always be transmitted,
even if the additional bits are all "0" and only the EOF symbol is
transmitted. This allows the decoder in the destination device to
distinguish what version of the protocol is being transmitted.
With regard to adding additional status information, the additional
status bits are allocated starting from the first available unused
least significant bit to reduce transmission time. If all 8 bits of
the status field become allocated, an additional field is added, as
described above, immediately prior to the existing status
field.
A receiver/decoder may be programmed to determine the version of
the received remote control message by examining the number of
fields and/or the number of bits in a particular field of data. By
determining the remote control message version in this manner,
current receiver/decoders can maintain forward compatibility, i.e.,
process future version of the present remote control message
protocol, and future receiver/decoders can maintain backward
compatibility, i.e., process past versions of the present remote
control message protocol.
Forward compatibility is maintained by designing the
receiver/decoder to process additional fields from future versions
of the protocol only for the purpose of calculating the checksum
and assume the last field to be the checksum byte. For example,
since the original version of the present remote control message
protocol contains 5 fields, receiver/decoders designed to process
only this version of the remote control message protocol would use
only the first four fields and disregard the remaining fields, but
would sum all of the field in the received remote control message,
including those after the first four, for the checksum and compare
the result to the checksum field. Future transmitters utilizing the
present remote control protocol should be designed to send the
checksum field last so earlier version receiver/decoders will
correctly process the basic message.
Backward compatibility is maintained by designing the
receiver/decoder to always check for earlier versions of the remote
control message protocol by examining the number of data fields
received and process the remote control message accordingly. If a
status bit is added to the original status field, then the polarity
of the new flag should be oriented such that an older version
remote, i.e., one that does not transmit the bit and thus defaults
it to "0", does not cause any unwanted action in the receiver.
As indicated above, the present remote control message protocol is
particularly suited for transmission in RF signal form, especially
during the pause intervals of IR remote control signal transmission
intervals. The waveforms defined above and their associated timing
ensure that the RF messages can be transmitted during such periods
without adversely affecting the IR transmission. The present
message protocol also allows additional types of data to be
transmitted and allows for expansion to accommodate increased
functionality, as well as permit forward and backward
compatibility. Further, the present message protocol provides for
security codes for preventing unwanted interference from other RF
remote controls.
A suitable receiver for detecting, decoding and processing the IR
and RF signals discussed above is now described. As shown in FIG.
12, suitable receiver 200 comprises controller 202 which receives
the IR and RF signals through IR signal receiver 208 and RF signal
receiver 210. Controller 202 decodes and processes the received
remote control signal and sends control signals to device mechanism
206 to perform the operation specified by the received remote
control signal. Device mechanism 206 comprises any one of a
plurality of components included in an electronic device that may
be controlled by the remote control signal. Such components
include, but are not limited to, RF tuners, VCR tape transport, DSS
transport decoder and TV tube deflection hardware. Controller 202
is also connected to memory 214 and display 204, which may include,
for example a front panel indicator for displaying the status of
the receiver, a set of indicator lights, an alpha-numeric display
or a display screen. The timing of controller 202 is controlled by
oscillator 212.
When an IR signal is directed at receiver 200, IR signal receiver
208 detects and provides the IR signal to controller 202.
Controller 202 decodes and processes the received IR signal based
on the appropriate IR format specification. Likewise, controller
202 receives RF signals via RF signal receiver 210 and decodes and
processes the received RF signal based on the appropriate RF format
specification. The elements of receiver 200 and their operation are
generally known in the art.
Receiver 200 may be designed to perform the receiving, decoding and
processing functions in a number of predetermined modes or modes
selected by a user. First, controller 202 may be programmed to
decode and process the IR and RF signals in the order that the
signals are received. In such a case, controller 202 sends the
necessary control signals to receiver mechanism 206 as the
respective remote control signals are detected.
Second, receiver 200 may be arranged to decode and process the
incoming signals according to a predetermined priority or a
priority selected by a user. For example, if IR signals are
selected as higher priority, controller 202 may be programmed to
ignore RF signals, or to store the RF signals for processing at a
later time if IR signals are present. Also, higher priority may be
given to a particular signal in the form of interrupting the
decoding process to service the higher priority signal. For
example, if IR signals are selected as higher priority, controller
202 may be programmed to temporarily stop processing RF signals
anytime an IR signal is detected. The priority selections may be
made using any conventionally known method, including, but not
limited to using an On Screen Display menu.
Receiver 200 may also be arranged to respond to only one type of
signal, or set of signals, and ignore other type of signals. For
example, if receiver 200 is programmed for use with only IR
signals, controller 202 would ignore all RF signals. Again,
receiver 200 may be selected to respond to or ignore particular
signals using conventional user interface methods. Although FIG. 12
shows IR signal receiver 208 and RF signal receiver 210, it is to
be understood that the receiver arrangements described above may be
implemented in a receiver having a plurality of signal receiver
types and any number of signal receivers.
Due to the repeated RF signal transmission intervals associated
with each user input and the possibility of interference corrupting
individual messages when the present remote control message
protocol is transmitted in RF form, a RF receiver/decoder
associated with the destination device should contain processing to
determine if a received message should be acted upon or ignored. A
suitable processing method is described below. Such a method may be
implemented on the RF receiver/decoder by programming a destination
device controller as known in the art. The present method allows
the RF receiver/decoder to distinguish new keypresses of remote
control 10 from old ones. This is necessary to prevent the RF
receiver/decoder from performing multiple responses to single
keypresses of the remote. The two basic inputs to the present
method are the timing from the last operation and the state of a
keypress status bit in the status field of the message protocol
described above.
The timing from the last operation is measured by two separate
timers, a short timer and a long timer. The timers may be
implemented in software or in hardware, e.g., as part of the
controller IC. The short timer determines if the repeated messages
from a single remote keypress have come to an end or if a message
is missing from the middle of a repeated sequence. The long timer
is used to determine if a keypress status bit should be checked.
The keypress status bit is a status flag that is toggled with each
keypress. Suitable timer values for the short timer are 4-6 mS and
for the long timer are 900-1100 mS.
The short timer is setup for a time that would not expire when a
repeated RF message is received, yet will expire if a message is
missing from the repeated sequence due to interference or a key
release. The long timer is setup for the period that the requested
function should be repeated if a remote key is held down
indefinitely. The timers are reset after the RF receiver performs
the requested operation from the remote and run until the receiver
processes a new valid RF command.
A flowchart for implementing the present method is shown in FIG.
13. After performing the operation from the previous RF message in
step 182, the RF receiver controller resets the long and short
timers in step 184 and waits for a new RF message. When a new RF
message is detected in step 186, the receiver controller determines
whether the long timer has expired in step 188. If so, the receiver
controller performs the operation of the new RF message. If not,
the receiver controller checks whether the short timer has expired
in step 190. If not, the receiver controller returns to step 186 to
detect a new valid RF message. If so, the receiver controller
checks whether the keypress status bit has toggled in step 192. If
so, the receiver controller performs the operation of the new RF
message. If not, the receiver controller returns to step 186 to
detect a new valid RF message. Therefore, it can be seen that the
operation for a new RF message is performed if the long timer has
expired or if the short timer has expired and the keypress status
bit in the RF message has toggled to indicate a new keypress.
The present remote control message protocol is suitable for use in
automatically detecting the message format wherein a detector is
programmed to automatically determine the format, or version, of
the message protocol based on the data transmission speed. Such an
automatic format sensing method advantageously utilizes the leading
zero suppression feature of the present remote control message
protocol. In the leading zero suppression technique, the first bit
transmitted is always a logic one, therefore, a signal receiver may
be adapted to determine the speed of data transmission by measuring
the width of the first symbol. Knowing that various data
transmission speeds correspond to various formats, the receiver and
associated processor may be adapted to automatically sense which
format is being received and adjust the decoding accordingly. In
the embodiment described above, controller 202 would be programmed
to automatically determine the incoming message format by measuring
symbol width 108 of the first symbol after start sequence 82 in
message 80.
The determination of data transmission speed need not be limited to
a determination based on a width measurement of the first symbol.
The structure of the present remote control message protocol is
based on symbol encoding of a basic time interval. Therefore, any
part of, or the entire message may be used to determine the data
transmission speed and format, for example, the EOF marker.
Specifically, if memory is available to store the entire message
without decoding in on the fly, many powerful signal processing
techniques can be used.
Adjusting the data transmission speed may be useful for allowing
faster formats for the future that are compatible with the existing
formats. However, it is to be understood that the present automatic
format sensing method is not limited to faster formats. A slower
speed implementation could also be used, for example, if the
implementation provided a cost advantage.
The speed values may be limited to discrete values or allowed to
vary over a continuous scale. In this regard, limiting the speed
values to discrete values may be more advantageous than allowing a
continuously varying scale for the pulse widths due to
environmental noise factors and pulse distortions in the
receiver.
It will be apparent to those skilled in the art that although the
invention has been described in terms of an exemplary embodiment,
modifications and changes may be made to the disclosed embodiment
without departing from the essence of the invention. For example,
remote control 10 may be of the universal remote control type which
is capable of controlling one of a plurality of designated
electronic devices according to a reference code, or other signal
format identifying information, selected by the user. The reference
code may be selected using for example, the direct, manual entry
method, the semi-automatic stepping entry method, the automatic
entry method, or any other suitable method of selecting and
entering a reference code. In that case, remote control 10 uses the
identifying information to generate the appropriate signal
associated with the particular manufacturer and model.
Therefore, it is to be understood that the present invention is
intended to cover all modifications as would fall within the true
scope and spirit of the present invention.
* * * * *